The present invention relates to a yarn processing nozzle, such as a texturizing nozzle, and of the type wherein the yarn passageway is supplied with a heated gaseous or vaporous treatment fluid during operation, and which is adapted to be laterally opened to facilitate yarn thread-up. The present invention further relates to a method of threading a nozzle of the described type.
Yarn texturizing nozzles are used in the production of man-made filament yarns with the yarn operating at high spinning speeds of, for example, 2,000 m/min and above, and with the texturizing nozzle also serving to forwardly convey the advancing yarn. The thread-up of a nozzle of the described type presents a major problem, and it has been common to draw the yarns into the nozzle with a suction gun. This is a rather time consuming operation, and there have been numerous attempts to simplify this threading operation, note for example U.S. Pat. No. 4,519,115 and EPO Published Application 65726. All of these methods and devices involve the drawing of the yarn into the nozzle, and the disadvantages of such methods are well known.
Also known are nozzles which are divided in an axial plane of the yarn passageway, note for example U.S. Pat. No. 3,854,177, so that the advancing yarn can be inserted into the nozzle from the side, i.e. laterally with respect to its advancing direction. However, in the known apparatus of this type, the geometry of the yarn passageway and the air supply duct, and particularly the opening of the internal ducts, are so impaired that it is not possible to accomplish a satisfactory texturing of the yarn.
The present invention is based upon the nozzle designs described, for example, in copending U.S. applications Ser. Nos. 821,260 now U.S. Pat. No. 4,697,947, and 853,713 now U.S. Pat. No. 4,724,588. These designs have proven themselves to be excellent in operation, however a disadvantage has remained with these nozzles when they are opened to permit lateral threading of the yarns. In particular, when threading the yarn, a clearly increased quantity of the heated treatment fluid exits from the opened yarn passageway, as a result of the then reduced back pressure. This increased flow not only hinders the insertion of the yarn, but it also leads to a sharp decrease of the temperature of the nozzle and the heater of the treatment fluid. As a result, after closing the nozzle, it takes several minutes to restore stable operating conditions. The stopping of the supply of the treatment fluid will not solve this problem, since the heater would then have to shut down to prevent a risk of overheating and damage, and this also would lead to a delay after start-up before the nozzle reaches its operating temperature at stable conditions.
It will be understood that the heater for heating the treatment fluid has only a limited range of operation. One limit to the range of operation is the energy transfer capacity of the heater, i.e., the heater can only transfer a limited amount of heat to the treatment fluid. Thus, if there is a large mass of fluid flowing through the heater, the temperature of the fluid cannot be maintained. During the threading-up operation, the pressure of the fluid downstream of the heater will drop substantially, and therefore, the throughput of the heater will increase substantially to an extent exceeding the maximum heat transfer capacity of the heater. Thus, the temperature will drop. The disadvantage is that it will take time to again reach stable operating conditions after threading up. The other limit to the range of operation of the heater depends on the maximum temperature. Therefore, the heating system is provided with a control to switch off the energy supply, before a temperature is reached which will cause damage to the system. During normal operation, the heater operates within this range, and there is a temperature sensor provided to control energy supply in such a way that the fluid temperature remains constant and the operating conditions remain stable. The stable operating conditions, however, are disturbed by providing the lateral opening. The present invention renders it possible to maintain the stable operating conditions of the heater during the thread up operating in such a way that the heater is at least maintained within the range of operation as defined above.
It is accordingly an object of the present invention to provide a yarn treatment nozzle and a method of threading the same, which avoids the above noted disadvantages of the prior systems.
It is a more particular object of the present invention to provide a yarn treatment nozzle and method of threading the same in which the temperatures of the nozzle and in the heater, and the temperature of the treatment fluid leaving the heater, are maintained substantially at their operating level, while the nozzle is opened for thread-up.
It is a further object to maintain the heater in the control operation by which the temperature of the treatment fluid is maintained at the level of the treatment operation.